S_2O_8~(2-)/ZrO_2-Al_2O_3的制备、表征及其催化合成富马酸二甲酯

采用浸渍-沉淀法制备出纳米固体超强酸催化剂S_2O_8~(2-)/ZrO_2-Al_2O_3,通过正交实验得到最佳制备条件:Al_2O_3质量分数2.0%,-15℃陈化24 h,浸渍液(NH_4)_2 S_2O_8浓度0.8 mol/L,焙烧温度650℃,焙烧时间3 h。用XRD、TEM、BET、TG-DTG和化学分析手段分析了S_2O_8~(2-)/ZrO_2～Al_2O_3的晶化过程、比表面积、含硫量和热稳定性。结果表明,在焙烧温度为500～650℃时制备的催化剂属纳米材料(粒径<41 nm),有较大比表面积和较好的热稳定性;富马酸二甲酯的最佳合成条件为:n(甲醇):n(富马酸)=6.0:1.0,S_2O_8~(2-)/ZrO_2- Al_2O_3用量1.5%,带水剂苯用量10 mL,反应时间4.0 h,催化剂重复使用6次,酯化率大于90%。

PREPARATION, CHARACTERIZATION AND PERFORMANCE OF NANOSOLID SUPERACID S2O28-/ZrO2-Al2O3 FOR SYNTHESIS OF DIMETHYL FUMARATE

Nanometer composite solid superacid catalyst S_2O_8~(2-)/ZrO_2-Al_2O_3 was prepared by an im- pregnation-precipitation method.The optimum preparation conditions were found as follows:2.0% Al_2O_3,ageing temperature-15℃,ageing time 24 h,0.8 mol/L(NH_4)_2S_2O_8,activation temperea- ture 650℃,and activation time 3 h.The crystallization process,specific surface area,sulphur con- tent and thermal stability of S_2O_8~(2-)/ZrO_2-Al~2O_3 were studied by XRD,TEM,BET,TG-DTG and chemical analysis.Based on the orthogonally-designed experiments,the optimum conditions for the synthesis of dimethyl fumarate were found as follows:molar ratio of carbinol to fumaric acid 6.0: 1.0,mass of the catalyst 1.5%(relative to the total mass ratio),10 mL benzene as water carrying reagent,and reaction time 4.0 h.The catalyst exhibited good stability with the conversion of acetic acid still up to 90% after 6 runs.